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MG MGA - Generator, Regulator or Battery?

So now that we are back on the road I have my first electrical problem.

The battery isn't charging or holding a charge.

After sitting for 2 days (rain) we got a break in the weather and wanted to go for a ride. Not enough juice to start up.

Endered up turning on the ignition, putting the car in reverse and getting a slight push down the drive, let off the clutch and she started up fine and we went for a lovely ride.

Since she ran for 20 miles without a problem I assume it isn't the original generator.

The regulator is new.

The battery is 2 years old.

Where do you suggest I start?

Russell
R Egge

Did it re-start? Original generator could have been rebuilt. Was the warning light on? If not, generator is fine. I would start with both a specific gravity test of each battery cell (cheap tool at any auto supply) along with a voltmeter held to the batteries. Is the voltage above 13v or so while running at +/- 2500 rpm?
Paul Hanley

Russell

You need to check that the regulator is set correctly (should cut over when voltage is about 14V - read the manual)
Just because the regulator is new does not mean it is set correctly.
dominic clancy

Russell. The first thing I would do is to disconnect the battery/batteries from the system and fully charge them. If you have the lead/acid type with the removable tabs for refilling the water level, the hygrometer that Paul mentions will let you know if the battery will accept a full charge.

When the battery is fully charged, let it sit for two days, the amount of time you mentioned it sat before giving you a problem, and reconnect the battery/batteries to the car's electrical system. Try to start the car. Good starter action and the engine starting indicates your battery/ies are in good condition and will hold a charge. When you turn on the ignition switch, but before pulling the starter pull, look to see the read charging light is on. If not, make a note of it as it might affect what can be wrong.

If the car starts, have an assistant run the engine up to about 1800 rpm and measure the voltage at the battery clamps--this is your system voltage being supplied by the generator and controlled by the voltage regulator. You should see 13.5-14.5 V. If so, shut off the engine, disconnect the ground cable battery clamp. Clip a test light to the battery clamp and keep it away from the battery terminal. With the ignition switch off, touch the probe end of the test light to the battery terminal. If the light illuminates, you have some form of drain on the electrical system such as a shorted out generator, stuck points on the voltage regulator, or a short in the wiring.

When you have done this procedure, post your results and we should be able to focus our efforts on the most probably cause of your problem. Now, we can only "shotgun it", tossing out ideas which are unfocused and not aimed at a discrete problem.

Les
Les Bengtson

Russell - For a method to test the generator seperately from the regulator, see my post on the T series (TD, TF) list under the thread titled 52 TD Battery Generator/Charging. Once you have confirmed that the engerator is working correctly (if it is), then Les' voltage check will tell you if the regulator is operating correctly. If it isn't, consider contacting Bob Jeffers at bobj20@adelphia.net about having him convert your dead regulator into a properly functioning solid state regulator. Good luck - Dave
David DuBois

Here you go - Factory instructions on how to keep the smoke in! :)

http://www.1978mgmidget.com/manuals_and_booklets.html

Cheers Ian F
Ian Fraser

Russell

You said... "Since she ran for 20 miles without a problem I assume it isn't the original generator."

The ignition uses a very small amount of power when the engine is running. So don't think the dynamo was charging just because you got home - you could have just been lucky.

I made a 150 mile trip on a full battery, with about 5/6 starts through the day and returned on head lights till their dim glow let me know we weren't charging. The engine/ignition was still fine!

As the car really only goes on MG runs, I use a battery conditioner a lot and am now convinced my charging system may well have been out for months before the above realisation!

A really simple check, apart from the ignition light, is to see if your headlights get brighter as the engine goes from tick over to say 2000 rpm.

Go through the checks in the manual and also check for any corrosion in and behind the regulator.

Happy hunting

Pete
Pete Tipping

This thread was discussed on 22/05/2006

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